Guido was first seen in October 1988 as a business contact of the graphic designer, Colin Russell. Over subsequent meetings, allegedly to discuss business, it became clear that Colin and Guido were attracted to each other. Eventually Colin plucked up the courage to make a pass at him, but was heartbroken to discover that Guido was already involved with another man named Des.

After seeking the advice of his friends in Walford, Colin decided to play things cool with Guido, by not actively chasing him and instead becoming the chased. The plan worked and it wasn't long before Guido had invited himself back to Colin's to spend the night. Soon after, Guido split with his boyfirend and moved in with Colin. Colin had been scarred by past relationships, so he was adamant that he was not going to be used by Guido as a mere stop gap. He wanted assurances that the relationship had a future and he began to demand more commitment from Guido. Guido on the other hand, was far more relaxed and wanted to take the relationship one stage at a time. Petty arguments erupted between the pair, instigated by Colin, whose demeanour was constantly changing from mild-mannered to belligerent, for no apparent reason. Guido was left bemused by this, but eventually Colin divulged that he was suffering from poor health and the worry was having a negative effect on his behaviour. Guido managed to persuade Colin to get a check up, after which it was revealed that he had been suffering from early symptoms of multiple sclerosis.

The following weeks were tough for Guido, as he tried to help his boyfriend come to terms with his illness. Colin assumed that Guido would now want nothing more to do with him, but Guido assured him that he was there for the long haul. However, over the following months, major differences in the pair's political view points began to surface. Colin's liberal opinions clashed with Guido's more conservative ones. Colin was furious when Guido reported Junior Roberts to the police for stealing some of his CDs. He felt that police involvement would only worsen any anti-social behaviour, whilst Guido felt that punishment was the only way to curtail the problem. Meanwhile, Guido was becoming annoyed with Colin's tendency to worry more for others than himself, namely Donna Ludlow, the unappreciative heroin addict who Colin was trying to reform. Their opposing opinions brought to the fore how little they shared in common. In addition, Colin couldn't shake the feeling that Guido was only staying with him out of pity and so in February 1989 he decided to leave Walford to stay with his brother in Bristol. Colin decided not to tell Guido he was going, but a surprise visit from his ex, Barry Clark, stalled his departure, and Guido arrived home to see Colin packed and ready to leave. Guido was furious that Colin was planning on leaving without saying goodbye, but Colin said that he needed some space and he asked Guido to look after his flat while he sorted his head out. He then left a perplexed Guido to ponder on where he went wrong and despite claiming that he would return, he never did.

After Colin's departure Guido was seen one last time when he allowed Donna to stay in his flat for one night, before throwing her out the next day for overstaying her welcome. After this Guido then disappeared and his exit was never shown.

Guido's exit scenes were filmed and due to air in February 1989. However, due to time constraints, the scenes had to be cut and so his exit was never aired. When Ian and Cindy moved into the flat some time later, many viewers expected them to find Guido still inside.